Phase behavior of monomeric mixtures and polymer solutions with soft interaction potentials

Wijmans, Christopher M.; Smit, Berend; Groot, Robert D.

doi:10.1063/1.1362298

Cited by 107 publications

(116 citation statements)

References 30 publications

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“…The difference in the strength of the nonbonded interactions is what mimics the difference between beads which represents groups of different nature (polar/apolar). The effective interaction parameter between water beads is usually derived from the compressibility of water at room temperature [95], while the repulsion parameters for a multicomponent system can be derived using the Flory-Huggins -parameters that represent the excess free energy of mixing [89,95,96]. It is however important to note that different authors have used slightly different sets of parameters.…”

Section: Empirical Coarse-grained Modelsmentioning

confidence: 99%

Mesoscopic models of biological membranes

Venturoli¹,

et al. 2006

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Phospholipids are the main components of biological membranes and dissolved in water these molecules self-assemble into closed structures, of which bilayers are the most relevant from a biological point of view. Lipid bilayers are often used, both in experimental and by theoretical investigations, as model systems to understand the fundamental properties of biomembranes. The properties of lipid bilayers can be studied at different time and length scales. For some properties it is sufficient to envision a membrane as an elastic sheet, while for others it is important to take into account the details of the individual atoms. In this review, we focus on an intermediate level, where groups of atoms are lumped into pseudo-particles to arrive at a coarse-grained, or mesoscopic, description of a bilayer, which is subsequently studied using molecular simulation.The aim of this review is to compare various strategies to coarse grain a biological membrane. The conclusion of this comparison is that there can be many valid different strategies, but that the results obtained by the various mesoscopic models are surprisingly consistent. A second objective of this review is to illustrate how mesoscopic models can be used to obtain a better understanding of experimental systems. The advantage of coarse-grained models is that these can be simulated very efficiently, so that phenomena involving large systems, or requiring a large number of simulations, can be studied in detail. This is illustrated with the study of the relation between the phase behavior of a membrane and the structure of the phospholipids, and the membrane structural changes due to molecules (such as alcohols, cholesterol and anesthetics) adsorbed to the membrane. We then discuss the effect of transmembrane peptides on the local structure of a membrane and the mechanism of vesicle fusion and fission.

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Section: Empirical Coarse-grained Modelsmentioning

confidence: 99%

Mesoscopic models of biological membranes

Venturoli¹,

et al. 2006

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“…(27), which arises from the use of a purely repulsive conservative force, is significant; without it there would be a one to one correspondence between a 11 and δ 1 , and between a 22 and δ 2 with a 12 then given by the geometric mean of a 11 and a 22 . Instead we must regard Eq.…”

Section: B Mapping Dpd Onto Regular Solution Theorymentioning

confidence: 99%

“…Instead we must regard Eq. (27) as a definition of a 12 . This is possible since all other parameters are in principle known: a 11 and a 22 could be determined from pure component compressibility data as suggested by GW, while α has been determined by the same authors to be approximately 0.1 for DPD densities ρr c 3 > 3.…”

Section: B Mapping Dpd Onto Regular Solution Theorymentioning

confidence: 99%

New parametrization method for dissipative particle dynamics

Travis

Bankhead

Good

et al. 2007

The Journal of Chemical Physics

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We introduce an improved method of parameterizing the Groot-Warren version of Dissipative Particle Dynamics (DPD) by exploiting a correspondence between DPD and Scatchard-Hildebrand regular solution theory. The new parameterization scheme widens the realm of applicability of DPD by first removing the restriction of equal repulsive interactions between like beads, and second, by relating all conservative interactions between beads directly to cohesive energy densities.We establish the correspondence by deriving an expression for the Helmoltz free energy of mixing obtaining a heat of mixing which is exactly the same form as that for a regular mixture (quadratic in the volume fraction) and an entropy of mixing which reduces to the ideal entropy of mixing for equal molar volumes. We equate the conservative interaction parameters in the DPD force law to the cohesive energy densities of the pure fluids providing an alternative method of calculating the self-interaction parameters as well as a route to the cross-interaction parameter.We validate the new parameterization by modelling the binary system: SnI 4 /SiCl 4 , which displays liquid-liquid coexistence below an upper critical solution temperature around 140˚C. A series of DPD simulations were conducted at a set of temperatures ranging from 0˚C to above the experimental upper critical solution temperature using conservative parameters based on extrapolated experimental data. These simulations can be regarded as being equivalent to a quench from a high temperature to a lower one at constant volume.Our simulations recover the expected phase behaviour ranging from solid-liquid coexistence to liquid-liquid co-existence and eventually leading to a homogeneous single -3-phase system. The results yield a binodal curve in close agreement with one predicted using regular solution theory, but, significantly, in closer agreement with actual solubility measurements.-4-

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“…N i = N During a simulation, the following trial moves are attempted: displacements, rotations, reptation, configurationalbias partial regrowths (only for partially flexible molecules), 60 volume changes, identity exchanges 61,62 (only for mixtures of linear chains), and coupling parameter changes. They are selected randomly but with a fixed probability proportional to the ratio 100:100:10:100:1:100:1000, respectively.…”

Section: Simulation Methodsmentioning

confidence: 99%

Isotropic-nematic phase equilibria of hard-sphere chain fluids—Pure components and binary mixtures

Oyarzún

Westen

Vlugt

2015

The Journal of Chemical Physics

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The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components. C 2015 AIP Publishing LLC. [http://dx

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Phase behavior of monomeric mixtures and polymer solutions with soft interaction potentials

Cited by 107 publications

References 30 publications

Mesoscopic models of biological membranes

Mesoscopic models of biological membranes

New parametrization method for dissipative particle dynamics

Isotropic-nematic phase equilibria of hard-sphere chain fluids—Pure components and binary mixtures

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